Tampons are inserted either digitally or by insertion means which generally take the form of an outer tube which surrounds the tampon pledget and a cooperating inner tube or plunger which pushes the tampon pledget from the bottom outward through the leading edge of the outer tube.
Tampon tubes are made either of cardboard or of plastic. Plastic molding tubes are extremely expensive and comparatively difficult to manufacture because of the necessity for injection molding the outer tube. Such tubes are generally designed with bullet-shaped leading edges formed by a series of petals which must be made free of flash to prevent injury to the user during insertion. This adds further to the expense of the tube manufacture and complication inherent in the manufacturing process.
Paper tubes, on the other hand, have been found to be less aesthetically pleasing, in the past.
Convolutely wound paper tubes are preferable to spirally wound tubes because of their ease of manufacture. One of the difficulties inherent in utilizing a convolutely wound tube is that the surface on the inner portion of the tube does not have the release properties, i.e., is comparatively high friction as opposed to the visible outer surface of the outer tube. This relatively high friction inner surface makes expulsion difficult. Because of the necessity of providing an area for adherence during the convolute winding step to preserve the tubular configuration, one surface of the rectangular tube blank has been typically coated with a heat sealable thermoplastic adhesive and while only a portion of that surface is used for adhesive purposes the remainder provides a comparatively high friction surface for a tampon expulsion.
U.S. Pat. No. 2,580,665 discloses the concept of convolutely forming a paper tube with thermoplastic surfaces in contact with each other. U.S. Pat. No. 4,077,408 discloses the concept of convolutely winding for a tampon tube while the concept of convolute winding in general is explained in U.S. Pat. No. 3,252,388.